1. Field of the Invention
The present invention relates to perforated sheet material and a dispensing system for dispensing the sheet material. More particularly, the present invention relates to perforated sheet material and a dispensing system for dispensing individual segments of the sheet material from a dispenser.
2. Description of Related Art
A number of different types of sheet materials can be dispensed from a source. Typically, these materials are wound into a roll either with or without a core to provide a maximum amount of material in a relatively small amount of space. Some examples of these materials include paper towels, tissue, wrapping paper, aluminum foil, wax paper, plastic wrap, and the like.
For example, paper towels are either perforated or are not perforated. Non-perforated paper towels are typically dispensed from dispensers by rotating a crank or moving a lever each time the user desires to remove material from the dispenser. Although these types of dispensers are effective at dispensing individual segments from sheets of material, a user must make physical contact with the crank or lever each time the user desires to dispense the sheet material from the dispenser. For example, during a single day id an extremely busy washroom, hundreds or even thousands of users may physically contact a dispenser to dispense paper toweling therefrom. This leads to possible transfer of germs and a host of other health concerns associated with the spread of various contaminants from one user to another.
Attempts have been made to limit the amount of user contact with a dispenser. For example, U.S. Pat. No. 5,630,526 to Moody, U.S. patent application Ser. No. 08/851,937, filed on May 6, 1997 (pending), and U.S. Pat. No. 5,335,811 to Morand, the entire disclosures of which are incorporated herein by reference, disclose systems for dispensing individual segments of sheet material from a roll of sheet material having perforated tear lines separating the individual segments. Pulling an end-most segment of the sheet material tears the end-most segment away from the remaining material along a perforated tear line separating the end-most segment from the remainder of the material. Dispensing systems of this type are known as xe2x80x9ctouch-lessxe2x80x9d because normally the user is not required to touch any portion of the dispenser itself. During dispensing, the user grasps only an end portion of the sheet material with one hand or both hands and pulls the sheet material from the dispenser.
With these touch-less types of dispensing systems, on any given attempt the result may fail to meet some of the desired criteria, and thus, cause some level of dissatisfaction. For example, a sheet may fail to separate fully along the first perforation tear line resulting in the dispensing of multiple sheets. In addition, the remaining sheet material end portion may not extend a sufficient distance from the dispenser outlet, requiring a user to subsequently dispense sheet material while touching the dispenser and thereby defeating its purpose. Alternatively, the remaining end portion may extend so far as to be unsightly and more susceptible to soiling. Lastly, the user may obtain substantially less than a full sheet of material when the tensioning forces applied by the dispenser in order to initiate separation along the perforation tear lines are greater than the strength of the material at the user/material interface. This last type of failure is known as tabbing.
Tabbing occurs more frequently when the sheet material is an absorbent material, such as a paper towel, and when the user grasps this absorbent material with one or more wet hands. Typically, the wet strength of such materials is less than 50% of the dry strength, and, more typically, is 15% to 30% of the dry strength. Thus, when the sum of the tensioning forces exerted on a sheet of absorbent material by a user with wet hands exceeds the wet strength of the material, tabbing is likely to occur. Further, the strength of most sheet materials, wet or dry, is not typically equal in all directions, but typically weaker in the cross machine direction, where machine direction refers to the manufacturing process orientation in the plane of the web and cross machine direction is orthogonal in the plane of the web to the process orientation.
Thus, it is desired to improve reliability of dispensing such that the user obtains a single, fully intact sheet which has separated cleanly and completely from the remaining material along the perforated tear line and where a sufficient length, typically about 2 to 4 inches, of the remaining end portion of sheet material extends from the outlet of the dispenser so as to be available for subsequent dispensing.
In light of the foregoing, there is a need in the art for improved sheet material and an improved dispensing system which increases reliability of single sheet dispensing of sheet material.
Accordingly, the present invention is directed to sheet material, a dispensing system, and a method that substantially obviate one or more of the limitations of the related art. To achieve these and other advantages and in accordance with the purposes of the invention, as embodied and broadly described herein, the invention in one aspect includes dispensable sheet material. The sheet material includes wet-formed sheet material having opposite side edges spaced apart from one another to define the overall width of the sheet material and zones of weakness spaced along the sheet material. The zones of weakness include a plurality of perforations and frangible sheet material portions. Each of the zones of weakness has a strength equivalent to that of a perforated tear line having a total width of the frangible sheet portions of from about 10% to about 30% of the overall width of the sheet material. The sheet material has an elasticity in the dispensing direction of from about 4% to about 20%. The sheet material has a dry tensile strength in the dispensing direction of from about 4,000 grams per 3 inches of width to about 12,000 grams per 3 inches of width. The sheet material has a wet tensile strength in the weakest direction, preferably in a direction orthogonal to the dispensing direction, of at least about 900 grams per 3 inches of width.
In another aspect, the present invention includes dispensable sheet material including dry-formed sheet material having opposite side edges spaced apart from one another to define the overall width of the sheet material. The sheet material includes zones of weakness spaced along the sheet material. The zones of weakness include a plurality of perforations and frangible sheet material portions. Each of the zones of weakness has a strength equivalent to that of a perforated tear line having a total width of the frangible sheet portions of from about 10% to about 30% of the overall width of the sheet material. The sheet material has an elasticity in the dispensing direction of from about 4% to about 20%. The sheet material has a dry tensile strength in the dispensing direction of from about 4,000 grams per 3 inches of width to about 12,000 grams per 3 inches of width.
In another aspect, the perforations and/or the frangible sheet material portions are nonuniform.
In another aspect, above 20% of each of the zones of weakness comprises frangible sheet material portions narrower in width and greater in frequency than the frangible sheet material portions in the remainder of each of the zones of weakness.
In still another aspect, the collective center of the centers of gravity of the frangible sheet material portions on at least one side of the center line of the sheet material is substantially closer to a separation initiation region of the sheet material than to a separation control region of the sheet material.
In an additional aspect, the frangible sheet material portions in a separation initiation region of the sheet material are narrower and greater in frequency than the frangible sheet material portions in a separation control region of the sheet material, and the percent difference between the percent bond of the separation initiation region and the percent bond of the separation control region is less than about 20%.
In another aspect, the ratio of the perforation width in the separation initiation region to the perforation width in the separation control region is less than about 90%.
In another aspect, the ratio of the average energy absorption capacity per bond in the control region to the average energy absorption capacity per bond in the initiation region is at least about 4.
In a further aspect, the present invention includes a dispensing system including a dispenser having an outlet for allowing sheet material to be dispensed from the dispenser.
In yet another aspect, the present invention includes a dispensing system wherein the width of the outlet of the dispenser is less than the overall width of the sheet material.
In an even further aspect of the invention, a method is provided to control the exposed length (length of the tail) of sheet material extending from the outlet of the dispenser when a user dispenses sheet material from the sheet material dispensing system. This method includes controlling initiation of separation of adjacent sheet material segments by providing the sheet material with a predetermined width of at least one separation initiation region having frangible sheet material portions narrower in width and greater in frequency than the frangible sheet material portions in at least one separation control region of the sheet material. The method also includes controlling the time to complete separation of adjacent sheet material segments by providing the separation control region of the sheet material with frangible sheet material portions wider in width and lower in frequency than the frangible sheet material portions in the separation initiation region of the sheet material.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.